Respiratory Gas Transport

Once the respiratory gases have diffused in the lungs, resulting in the blood becoming O₂ rich and CO₂ being exhaled, the next stage of transporting the O₂ rich blood to the tissues that need it takes place. 

At the same time the next batch of CO₂ rich blood must be brought to the lungs for the process to take place again.

The transportation of gases throughout the body takes place in the bloodstream through the action of the cardiovascular system (heart and blood vessels), as can be seen in the adjacent image. 

Oxygenated blood leaving the lungs flows back to the heart via the pulmonary veins and is then pumped to the rest of the body from the left ventricle via the aorta and its branches .

The amount of haemoglobin (Hb) in the blood determines its oxygen carrying capacity.

Increases in CO₂, H+ ions or temperature will also decrease the ability of O₂ to bind to Hb.

This in turn leads to a decrease in performance as less O₂ means less production of energy through aerobic metabolism.

As the oxygen rich blood reaches the capillaries gas exchange occurs, oxygen is delivered to the tissues and de-oxygenated blood (loaded with CO₂) leaves the tissues of the body and flows back to the heart where it is pumped to the lungs via the pulmonary arteries.

Once CO₂ is transported to the lungs it diffuses out of the capillaries into the alveoli and exhaled out of the lungs.